《传感器技术与应用》课件第六章热电式传感器

《传感器技术与应用》课件第六章热电式传感器热电式传感器是一种常用的温度传感器，利用两个不同金属的热电势差随温度的变化而变化。本章将介绍热电式传感器的原理、类型、优缺点和应用，以及相关测量技术、误差和校准方法。ThermoelectricPrinciple1SeebeckEffectWhentwodifferentmetalsarejoinedtogether,atemperaturedifferencebetweenthetwojunctionscreatesanelectromotiveforce(EMF)inthecircuit.2PeltierEffectWhenacurrentflowsthroughajunctionoftwodifferentconductors,heatisabsorbedorreleaseddependingonthedirectionofthecurrent.3ThomsonEffectWhenatemperaturegradientexistsalongaconductor,acurrentisgeneratedinthedirectionperpendiculartoboththetemperaturegradientandthedirectionofcurrentflow.TypesofThermocouplesNobleMetalThermocouplesArethemostaccurateandstable,andareusedinhigh-temperatureapplicationssuchasfurnaces,ovens,andkilns.BaseMetalThermocouplesArecheaperandhaveawidertemperaturerange,butarelessstableandaccurate.Theyareusedinprocesscontrol,HVAC,andotherindustrialapplications.SinteredMetalThermocouplesAremadebycompressingmetalpowdersintoaspecificshape.Theyhavefastresponsetimesandareusedinhigh-temperatureandhigh-pressureenvironments.DesignandConstructionofRTDsMaterialPlatinumisthemostcommonmaterialusedinRTDsduetoitsstabilityandrepeatability.ConstructionRTDsconsistofalong,thinwirewoundaroundaceramiccore.Thewire'sresistancechangeswithtemperature.ApplicationsRTDsareusedinprecisetemperaturemeasurementapplicationssuchaslabequipment,medicaldevices,andaerospacetechnology.TypesofThermistors1NegativeTemperatureCoefficient(NTC)Theresistancedecreasesasthetemperatureincreases.Theyareusedinautomotive,homeappliance,andHVACapplications.2PositiveTemperatureCoefficient(PTC)Theresistanceincreasesasthetemperatureincreases.Theyareusedintemperaturesensors,heatingelements,andmotoroverheatprotection.InfraredTemperatureSensorsThermopileSensorsArecomprisedofmultiplethermocoupleswhichdetecttheinfraredradiationemittedbyanobjectandconvertitintoatemperaturereading.PYROMETERSUseasinglethermocoupletomeasurethetemperatureofanobjectbycomparingthetemperaturesattwodifferentwavelengths.TypesofPyrometersOpticalPyrometerMeasuresthetemperatureofveryhotobjectsthroughitscolor,orspectralradiationintensity.InfraredPyrometerMeasuresthetemperatureofhotobjectsbydetectingtheinfraredradiationtheyemit.Thermo-LuminescentRadiationPyrometerMeasuresthetemperatureofobjectsbydetectingthelighttheyemitwhenheated.ApplicationsofThermocouples1IndustrialSettingsUsedinindustrialprocessessuchaschemicalprocessing,oilandgasrefining,andpowergenerationfortemperaturemonitoringandcontrol.2FoodIndustryUsedfortemperaturemonitori